Rate of rejuvenation of the skeleton

Abstract

Radioactive P was administered, as Na phosphate, to rabbits, rats and frogs and, after the lapse of a certain time, the activity of 1 mg. bone inorganic P compared with that of 1 mg. plasma inorganic P. Within 50 days, 29% of the femur and tibia epiphysis were found to be renewed, while the corresponding figure for the diaphysis amounted to 7%. Only half of the mineral con-stituents of the scapula were found to be unchanged. The phosphatides of the bones and the marrow were entirely renewed.[long dash]The P of the apical part of the dentine of the rabbit''s incisor was found to have the same activity as the plasma P. Thus this part of the dentine was grown with the participation of labelled plasma during the expt. The greater part of the incisal end of the dentine was not formed by a calcification process in situ but by a slip of the apical part of the dentine.[long dash]No interaction of any significance took place between the incisal part of the enamel and the dentine either under their formation or at a later date.